Per @each, skipping cleanup of (|nsec_|nsec3_)origin nodes in
qpznode_release in qpzone.c is a residual from RBTDB, but it is
unnecessary or at most a performance optimization with QP.
Remove it to make it further changes easier to qpznode_release easier.
> Put a space before opening parentheses only after control statement
> keywords (for/if/while...) except this option doesn’t apply to ForEach
> and If macros. This is useful in projects where ForEach/If macros are
> treated as function calls instead of control statements.
As the qpcache has only one active header at the time, we can move the
SIEVE-LRU members from dns_slabheader_t to dns_slabtop_t structure thus
saving a little bit of memory in each slabheader and using it only once
per type.
The code that combines the top-level hierarchy (per-typepair) and
individual slab headers (per-version) saves a little bit of memory, but
makes the code convoluted, hard to read and hard to modify. Change the
top level hierarchy to be of different type with individual slabheaders
"hanging" from the per-typepair dns_slabtop_t structure.
This change makes the future enhancements (changing the top level data
structure for faster lookups; coupling type + sig(type) into single
slabtop) much easier.
The slabheader doesn't directly attach or link to 'db' anymore. Pass
only the memory context needed to create the slab header to make the
lack of relation ship more prominent.
Also don't call dns_slabheader_reset() from dns_slabheader_new(), it has
no added value.
The slabheader.c, qpzone.c and qpcache.c had couple of shared macros
that were copied and paste between the units. Move these common
attributes access macros into private header, so these can be shared
among the three compilation units.
In the dns_qpcache unit, we use EXISTS() macro, but in the dns_qpzone
there's a NONEXISTENT() macro for the same slabheader attribute. Unify
the macro to be also EXISTS() in dns_qpzone.
Previously, when a negative header was stored in the cache, it would be
stored in the dns_typepair_t as .type = 0, .covers = <negative type>.
When searching the cache internally, we would have to look for both
positive and negative typepair and the slabheader .down list could be a
mix of positive and negative types.
Remove the extra representation of the negative type and simply use the
negative attribute on the slabheader. Other units (namely dns_ncache)
can still insert the (0, type) negative rdatasets into the cache, but
internally, those will be converted into (type, 0) slabheaders, and vice
versa - when binding the rdatasets, the negative (type, 0) slabheader
will be converted to (0, type) rdataset. Simple DNS_TYPEPAIR() helper
macro was added to simplify converting single rdatatype to typepair
value.
As a side-effect, the search logic in all places can exit early if
there's a negative header for the type we are looking for, f.e. when
searching for the zone cut, we don't have to walk through all the
slabheaders, if there's a stored negative slabheader.
Use dns_rdatatype_none instead of plain '0' for dns_rdatatype_t and
dns_typepair_t manipulation. While plain '0' is technically ok, it
doesn't carry the required semantic meaning, and using the named
dns_rdatatype_none constant makes the code more readable.
The RR type 0 is a reserved type for SIG[1] resource record. It should
not be ever inserted into the database nor queried. Add a special
handling to bail out quickly with DNS_R_DISALLOWED when inserting and
ISC_R_NOTFOUND when looking up TYPE0. This is also prerequisite for
stricter checks in the follow-up commit.
1. https://www.rfc-editor.org/rfc/rfc2535#section-4.1.8.1
The dns_typepair_t and dns_rdatatype_t variables were both named 'type'
in multiple places. Rename all dns_typepair_t variables to include word
'pair' in the variable name to make sure that the distinction between
the two types is more clear.
All databases in the codebase follow the same structure: a database is
an associative container from DNS names to nodes, and each node is an
associative container from RR types to RR data.
Each database implementation (qpzone, qpcache, sdlz, builtin, dyndb) has
its own corresponding node type (qpznode, qpcnode, etc). However, some
code needs to work with nodes generically regardless of their specific
type - for example, to acquire locks, manage references, or
register/unregister slabs from the heap.
Currently, these generic node operations are implemented as methods in
the database vtable, which creates problematic coupling between database
and node lifetimes. If a node outlives its parent database, the node
destructor will destroy all RR data, and each RR data destructor will
try to unregister from heaps by calling a virtual function from the
database vtable. Since the database was already freed, this causes a
crash.
This commit breaks the coupling by standardizing the layout of all
database nodes, adding a dedicated vtable for node operations, and
moving node-specific methods from the database vtable to the node
vtable.
Is there a time when new_qp(c|z)node() would not be followed by
assignment of the namespace? No, so let's add the assignment to the
function that creates the node.
Now that we have to code working, rename 'dns_qp_lookup2' back to
'dns_qp_lookup' and adjust all remaining 'dns_qp_lookup' occurrences
to take a space=0 parameter.
For now we only allow DNS_DB_NSEC_* values so it makes sense to change
the type to an enum.
Rename 'denial' to the more intuitive 'space', indicating the namespace
of the keyvalue pair.
The dbiterator can take three modes: full, nsec3only and nonsec3.
Previously, in full mode the dbiterator requires special logic to jump
from one qp-trie to the other. Now everything is in one trie, other
special logic is needed.
The qp-trie is now sorted in such a way that all the normal nodes come
first, followed by NSEC nodes, and finally the NSEC3 nodes. NSEC nodes
are empty nodes and need to be skipped when iterating.
We add an additional auxiliary node to the trie, an NSEC origin, so
we can easily find the point in the trie where we need to continue
iterating.
In preparation to merge the three qp tries (tree, nsec, nsec3) into
one, add the piece of information into the qpkey. This is the most
significant bit of information, so prepend the denial type to the qpkey.
This means we need to pass on the denial type when constructing the
qpkey from a name, or doing a lookup.
Reuse the the DNS_DB_NSEC_* values. Most qp tries in the code we just
pass on 0 (nta, rpz, zt, etc.), because there is no need for denial of
existence, but for qpzone and qpcache we must pass the right value.
Change the code, so that node->nsec no longer can have the value
DNS_DB_NSEC_HAS_NSEC, instead track this in a new attribute 'havensec'.
Since we use node->nsec to convert names to keys, the value MUST be set
before inserting the node into the qp-trie.
Update the fuzzing and unit tests accordingly. This only adds a few
extra test cases, more are needed.
In the qp_test.c we can remove test code for empty keys as this is
no longer possible.
RRset ordering is now an enum inside struct rdataset attributes. This
was done to keep size to of the structure to its original value before
this MR.
I expect zero performance impact but it should be easier to deal with
attributes in debuggers and language servers.
Qpzone employs a locking strategy where rwlocks are grouped into
buckets, and each zone gets 17 buckets.
This strategy is suboptimal in two ways:
- If named is serving a single zone or a zone is the majority of the
traffic, this strategy pretty much guarantees contention when using
more than a dozen threads.
- If named is serving many small zones, it causes substantial memory
usage.
This commit switches the locking to a global table initialized at start
time. This should have three effects:
- Performance should improve in the single zone case, since now we are
selecting from a bigger pool of locks.
- Memory consumption should go down significantly in the many zone
cases.
- Performance should not degrade substantially in the many zone cases.
The reason for this is that, while we could have substantially more
zones than locks, we can query/edit only O(num threads) at the same
time. So by making the global table much bigger than the expected
number of threads, we can limit contention.
In the current implementation, the resigning heap is part of the zone
database. This leads to a cycle, as the database has a reference to its
nodes, but each node needs a reference to the database.
This MR splits the resigning heap into its own separate struct, in order
to help breaking the cycle.
Recovering the node lock from a pointer to the header and a pointer to
the db is a common operation. This commit abstracts it away into a
function, so that the node lock selection logic may be modified more
easily.
previously, ISC_LIST_FOREACH and ISC_LIST_FOREACH_SAFE were
two separate macros, with the _SAFE version allowing entries
to be unlinked during the loop. ISC_LIST_FOREACH is now also
safe, and the separate _SAFE macro has been removed.
similarly, the ISC_LIST_FOREACH_REV macro is now safe, and
ISC_LIST_FOREACH_REV_SAFE has also been removed.
Profiles show that an high amount of CPU time spent in memset.
By removing zero initalization of certain large buffers we improve
performance in certain authoritative workloads.
the pattern `for (x = ISC_LIST_HEAD(...); x != NULL; ISC_LIST_NEXT(...)`
has been changed to `ISC_LIST_FOREACH` throughout BIND, except in a few
cases where the change would be excessively complex.
in most cases this was a straightforward change. in some places,
however, the list element variable was referenced after the loop
ended, and the code was refactored to avoid this necessity.
also, because `ISC_LIST_FOREACH` uses typeof(list.head) to declare
the list elements, compilation failures can occur if the list object
has a `const` qualifier. some `const` qualifiers have been removed
from function parameters to avoid this problem, and where that was not
possible, `UNCONST` was used.
dns_zonekey_iszonekey() was the only function defined in the
dns_zonekey module, and was only called from one place. it
makes more sense to group this with dns_dnssec functions.
the step() function (used for stepping to the prececessor or
successor of a database node) could overlook a node because
there was an rdataset marked IGNORE because it had been rolled
back, covering an active rdataset under it.
The short convenience list macros were used very sparingly and
inconsistenly in the code base. As the consistency is prefered over
the convenience, all shortened list macro were removed in favor of
their ISC_LIST API targets.
the target buffer passed to dns_name_concatenate() was never
used (except for one place in dig, where it wasn't actually
needed, and has already been removed in a prior commit).
we can safely remove the parameter.
The offsets were meant to speed-up the repeated dns_name operations, but
it was experimentally proven that there's actually no real-world
benefit. Remove the offsets and labels fields from the dns_name and the
static offsets fields to save 128 bytes from the fixedname in favor of
calculating labels and offsets only when needed.
Acquire the database refernce in the detachnode() to prevent the last
reference to be release while the NODE_LOCK being locked. The NODE_LOCK
is locked/unlocked inside the RCU critical section, thus it is most
probably this should not pose a problem as the database uses call_rcu
memory reclamation, but this it is still safer to acquire the reference
before releasing the node.
The function name dns_slabheader_fromrdataset() was too similar
to dns_rdataslab_fromrdataset(). Instead, we now have an rdataset
method 'getheader' which is implemented for slab-type rdatasets.
A new NOHEADER rdataset attribute is set for rdatasets using
raw slabs (i.e., noqname and closest encloser proofs); when
called on rdatasets with that flag set, dns_rdataset_getheader()
returns NULL.
when dns_rdataslab_fromrdataset() is run, in addition to
allocating space for a slab header, it also partially
initializes it, setting the type match rdataset->type and
rdataset->covers, the trust to rdataset->trust, and the TTL to
rdataset->ttl.
there are now two functions for creating an rdataslab from an
rdataset: dns_rdataslab_fromrdataset() creates a full slab (including
space for a slab header), and dns_rdataslab_raw_fromrdataset() creates
a raw slab.
- there are now two functions for getting rdataslab size:
dns_rdataslab_size() is for full slabs and dns_rdataslab_sizeraw()
for raw slabs. there is no longer a need for a reservelen parameter.
- dns_rdataslab_count() also no longer takes a reservelen parameter.
(currently it's never used for raw slabs, so there is no _countraw()
function.)
- dns_rdataslab_rdatasize() has been removed, because
dns_rdataslab_sizeraw() can do the same thing.
- dns_rdataslab_merge() and dns_rdataslab_subtract() both take
slabheader parameters instead of character buffers, and the
reservelen parameter has been removed.
The dns_slabheader object uses the 'next' pointer for two purposes.
In the first header for any given type, 'next' points to the first
header for the next type. But 'down' points to the next header of
the same type, and in that record, 'next' points back up.
This design made the code confusing to read. We now use a union
so that the 'next' pointer can also be called 'up'.
in some places there were checks for failures of dns_qp_insert()
after dns_qp_getname(). such failures could only happen if another
thread inserted a node between the two calls, and that can't happen
because the calls are serialized with dns_qpmulti_write(). we can
simplify the code and just add an INSIST.
prio_type was being used in the wrong place to optimize cname_and_other.
We have to first exclude and accepted types and we also have to
determine that the record exists before we can check if we are at
a point where a later CNAME cannot appear.
Instead of using on hash of the name modulo number of the buckets,
assign the locknum randomly with isc_random_uniform(). This makes
the locknum assignment aligned with qpcache and allows the bucket
number to be non-prime in the future.
